When we stand before God, worshiping in dance, we are like a glass window. Others are able to see through us and view God. Our praise invites Him to shine through us. However, if we are living impure lives (in thought, speech, actions etc), then our glass becomes cloudy, and instead of seeing God, our own flesh becomes on display. This does not mean we need to be perfect, for none of us are, but we can surrender perfectly. By yielding to God, letting Him work on those things He wants to in our lives, by confessing and repenting of our sins which we knowingly do, we walk in the righteousness He has provided for us. We become pure.